Federal Agencies’ Use of the Social Costs of Greenhouse Gases in NEPA Analysis

The social cost of greenhouse gas estimates are useful for quantifying climate impacts in analyses conducted under the National Environmental Policy Act (NEPA). Although the Interagency Working Group (IWG) social costs of greenhouse gases metrics were originally developed for use by federal agencies in rulemakings, the metrics are applicable for project-level determinations under NEPA, and have been used in some evaluations of projects and plans. 

Currently, though some agencies have used the social costs of greenhouse gases in NEPA analysis, no agency regularly uses the metric in environmenta impact statements or envirornmental assessments, but this may change as a result of recent guidance. 1  A number of other agencies, however, have never used the tool despite evaluating projects with major greenhouse gas effects. Below are examples of when agencies have or should have applied the social cost metrics in NEPA analysis to assess a project’s climate impacts.

This page was last updated on April 5, 2021. Please contact iliana.paul@nyu.edu with any questions.

Regularly Use

Lead Agency	Examples
None	None

Occasionally Use 2

Lead Agency	Examples
	Used Rulemaking for Colorado Roadless Areas (2016) Did Not Use Pine Mountain Late-Successional Reserve Habitat Protection and Enhancement Project (2017)
	Used Missouri River Recovery Management Plan (2016) Did Not Use Pebble Mine Environmental Impact Statement (2020)
	Used Stream Protection Rule (2016) Did Not Use San Juan Mine Deep Lease Extension Mining Plan Modification (2019) Western Energy Company's Rosebud Mine Area F (2018)
	Used Little Willow Creek Protective Oil and Gas Leasing (2015) Oil and Gas Lease Parcel, October 21, 2014 Sale (Miles City Field Office) (2014) Did Not Use Coastal Plain (Alaska Wildlife Refuge) Oil and Gas Leasing Program (2019) Eastern Colorado Resource Management Plan (Draft 2019)
	Used U.S. DOT/NHTSA - Draft Environmental Impact Statement, Corporate Average Fuel Economy Standards, Passenger Cars and Light Trucks, Model Years 2017-2025 (Draft 2011)
	Used Navajo Generating Station-Kayenta Mine Complex Project (2016)
	Used Liberty Development and Production Plan (2017) Gulf of Mexico OCS Oil and Gas Lease Sale: 2017 Central Planning Area Lease Sale 247 Final Supplemental Environmental Impact Statement (2016) Outer Continental Shelf Oil and Gas Leasing Program:2017-2022 (2016) Cook Inlet Planning Area Oil and Gas Lease Sale 244 (2016)

Never Use 3

Lead Agency	Examples
	Generic - License Renewal of Nuclear Plants Supplement 56 Regarding Fermi 2 Nuclear Power Plant, NUREG-1437 (2016)
	Juneau Access Improvements Project (2018) I-15, Payson Main Street Interchange (2018)
	Annova LNG Brownville Project (2018) Rio Grande LNG Project (2019)

1. To date, no agencies default to using the Interagency Working Group (IWG) social costs of greenhouse gases metric in NEPA analysis documents with significant greenhouse gas emissions effects (~ 1,000,000 metric tons of carbon dioxide annually); however, this will likely change as a result of recent guidance issued by the Biden Administration. See Exec. Order 13,990, 86 Fed. Reg. 7037 (Jan. 25, 2021).  ↩︎
2. These examples compile NEPA analyses (environmental impact statements or environmental assessments) in which an agency used the IWG social costs of greenhouse gases to assess a project’s climate impacts. ↩︎
3. These examples compile NEPA analyses (environmental impact statements or environmental assessments) for projects with significant greenhouse gas emissions, see note 1, in which agencies did not use the social cost metrics or rejected their suitability for assessing a project’s climate impacts. ↩︎